Volatile Compounds and Quality Characteristics of Fresh-Cut Apples and Mixed Fruits Coated with Ascorbic Acid during Cold Storage

Round 1

Reviewer 1 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The novelty and value of the resubmitted manuscript has been considerably improved (compared to the previous version) by including the data on aroma volatiles composition. The study has demonstrated a clear shift from the initial profile with prevalent apple and fruity aroma compounds (e.g. propyl propanoate and ethyl isovalerate) with fresh notes (hexanol) to the unpleasant off-odor (e.g. methanethiol and ethyl acetate). It should be noted that while ethyl acetate is described in the Table 1 generally favorably as a fruity aroma compound, its elevated level is associated with off-odor in apples (see Wright et al., 2015. The Journal of Horticultural Science and Biotechnology, 90(1), pp.1-13; Schmidt et al., 2020, Scientia Horticulturae, 262, p.109039).  Interestingly, this shift happened rather early during the shelf life and depended on storage temperature. The aroma shift day can be defined as the end of product's "flavor life" (postharvest life based on flavor) that is typically shorter than the life based on appearance or texture. See Kader, 2008, Journal of the Science of Food and Agriculture, 88(11), pp.1863-1868. I would recommend addressing this aspect in the paper; it would greatly increase its scientific value. For that purpose, the authors may need defining the product life duration based on appearance (e.g. reaching certain level of browning index or lightness) and/or texture, and the "flavor life". Wile at 15°C the flavor life is just 1 day and at 8°C probably 3 days (at day 4 some residual propyl propanoate is present), accurate determining flavor life at 4°C demands more data. Meantime, according to the Fig. 10 it is sometime between day 3 (good apple aroma) and day 9 (deteriorated odor). Additional work may be needed to determine the aroma shift day more accurately, but if possible, it is worth to do these efforts.
Some corrections: kumquat (Citrus japonica) and orange (C. sinensis) are different species, so don't call these fruit "orange", just use the word kumquat; when mentioned for the first time, refer to the scientific Latin name.
In the Table 1 the descriptors for 1-hexanol are most probably "grassy" and "green", not "frassy" and "freen", as written there.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Comments to authors

Title

The title of the manuscript does not properly reflect the content. Correlation between quality characteristics and volatile compound changes is not the main thrust of the study and should not take centre stage in the title. A form of treatment was applied to the apples prior to cold storage and this was not reflected in the title. Virtually all the analysis performed on fresh-cut apples were also performed on the mixed fruits. In my opinion, the title should be modified to reflect these comments. For example, it could read: Volatile compounds and quality characteristics of fresh-cut apples and mixed fruits coated with ascorbic acid during cold storage.  

Abstract

Revise/ rewrite the abstract to include some numerical values of the results from the study.

Introduction

There are lots of grammatical errors in the introduction and a few have been mentioned below. Revise the entire manuscript for grammar, and if possible, send it for proofreading by a native speaker.

Line 32: Revise to read “Fresh agricultural products…. for their……”

Lines 34-36: Revise for grammar

Lines 46-48: Expatiate more on the use of ascorbic acid coating since it is the main treatment in the current study. Summarise some studies on their importance, possible challenges that arise with its use that warrants combination of ascorbic acid coating and cold storage.

Lines 63-65: This does not reflect the content. Ascorbic acid coating was employed as the main treatment, but it is not reflected here. Revise to include this.

Lines 65-67: Revise for grammar  

Materials and methods

Lines 76 – 77: What do you mean by distribution by refrigerated food truck? This is not clear.

Lines 79 – 81: It is not clear if the mixed samples were also coated with ascorbic acid. For proper comparison and correlation between the apple and mixed fruit, there should be similar treatment levels between them.

A control (fresh-cut apples without ascorbic acid coating) is missing in the experimental design. This has to be included.

Line 89: Revise for grammar.

Lines 91 – 92: Revise to read “The sample moisture content was calculated as percentage wet basis using the following equation”

Lines 94 – 95: How do you perform total soluble solids? It should rather be measured. Expatiate/explain how it was measured.

Revise the use of the word “Moreover” throughout the manuscript. It is repetitive and in most instances, there is no need for its use.

Lines 101-103: Revise.

Virtually all the analysis performed on fresh-cut apples were also performed on the mixed fruits, yet, the subsections of the materials and methods section mentions only fresh-cut apples. Overall, the materials and methods section is poorly written, and the authors are advised to read research articles in standard journals and apprise themselves of the writing styles for the methodology section.

 

Results and Discussions

The results and discussion section is very shallow and the authors merely outlined the results from the study without proper discussions on the science behind the results. Appropriate and proper comparison with the results of other similar/related studies is also lacking. More in-depth discussion is needed.

 

Conclusions

The conclusions should be revised to include/reflect the implications of the results/study for the food industry.

 

The figures are barely legible. Their size and resolution should be enhanced and their titles modified to include the mix fruit samples.

Comments on the Quality of English Language

There are concerns with language and grammar that would require proofreading by a native speaker.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

I have a few minor comments on the PDF of the manuscript file. Please, see the attached file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Sentence pattens can be changed moderately.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

The paper Volatile Compounds Changes and Quality Characteristics Correlation of Fresh-Cut Apples during Distribution in Real-time Cold Chain Systems Applications in this form not is suitable for publication to Agriculture Journal since in many parts the paper is lack and many activities conducted during the trial are questionable.

I don’t read a novelty in this paper moreover there are in the materials and methods some approach questionable.

In first the storage period and temperature incompatible with a fresh cut product. Moreover, not is clear if the product was put in sealed or not sealed tray.

To put the fresh-cut apple with two not fresh-cut product, without explain why is questionable.

Not is clear the objective to record the temperature changes during distribution and storage if storage the product at not property temperature.

 

Below some information, to improve the paper first the new submission.

 

Title need to be rewrite. The title is not appropriate with information reported in the text

Some important data should be listed in the Abstract.

The introduction necessity to be rewrite and improve with specific focus on fresh-cut apple and analysis conducted during the trial. Many sentences are not supported by references or are inappropriate for the fresh-cut apple.

The temperature range adopted for stored the product is inappropriate since the microbiological growth is very high. The Authors not considered this critical aspect for this product that generally, in over the world, is stored in range 0-4 °C until to 8 ° not over 7-10 days. This limit is correlated with fast microbiological grown inside the packaging in function of the different temperature adopted during the storage.

The aim need to explain with a real and new advanced in the research contest.

The 2.1 paragraph is confused and need to be rewrite. I suggest to report the number of samples prepared for each treatment and storage time.

If the sample was sealed please report the material used for sealed the cup, with all specific characteristic of the film use (number of µm, permeability coefficient to O₂ and to CO₂ etc.)

If sealed inside the cup the atmosphere change. The Authors don’t have consider this aspect. Why?

To stored a fresh cut product sealed in a cup for 30 day or 10 at 15 °C is r

For each instrument or material used during the trial report all information (Instrument Name, Name of Company, City, State)

The constant level of microbial count during the storage, after few days for each temperature storage, around or over limit (https://doi.org/10.1007/s10068-021-00974-0)  is achieved as a result of high CO2 concentrations inside the packaging (https://doi.org/10.1016/S0925-5214(02)00005-4)

In Figure 1 need to change the ordinate value in different range in order to help the reader (i.e Moisture content better range 80-90 respect the range 60-90). The same for pH value, Titratable acidity and Total soluble solid

Report the force in N

L42 I don’t understand this sentence

L45 Better to report a review about these treatments or improve the references with other papers

L51 I think that these references are not appropriate for the fresh cut apple

L52 References are required

L57 References are required

L132 ..volatile compounds were analyzed by electronic nose (E-nose) or a fast gas chromatography-flame ionization detection (GC-FID) instrument. Why or one or the other? on what basis was the choice made?

Check and improve the caption with all the information and the abbreviations meaning.

 

 

Comments on the Quality of English Language

An English Language Editing service is suggested.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report (Previous Reviewer 2)

Comments and Suggestions for Authors

The authors have followed the recommendations, and the manuscript can be recommended for publication upon minor editorial changes. In particular, the sentence in l. 305-307 sounds controversially. I would propose the following edition of this sentence: "In general, ethyl acetate is described favorably as a fruity aroma compound (Table 1), but its elevated level is associated with off-odor in apples [35,36]". Some additional minor corrections are proposed in the "Language quality" section below.  

Comments on the Quality of English Language

Minor language changes might be recommended. In the newly added section in l. 310-314 keep using Past tense, similar to the rest of the Results section. For example, put "At 15°C the flavor life was just 1 day..." instead of "is", as well as in the subsequent two sentences. What does it mean "due to the resent of propyl propanoate" (l. 311)? Did you mean something like "according to the decrease of propyl propanoate"? I would add also "and accumulation of methanethiol". Start a new paragraph with the words "Detailed changes... etc." (now l. 300).  

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

Comments to authors

General

The authors should learn to respond to reviewers’ comments in a tabular form separately, prior to making the corrections on the manuscript. This way, the authors could have the opportunity explain why some suggestions/comments were not attended to.

Introduction

The introduction is still riddled with grammatical/structural errors. There is no proper flow between paragraphs as they are disjointed. My earlier suggestion still stands. The manuscript requires proof reading by a native speaker.  

Line 32: Revise to read “Fresh agricultural products…. for their……”

Lines 34-36: Revise for grammar

Lines 46-47: The use of ascorbic acid in fresh-cut apples can be found currently in Korean markets. I do not understand this. Revise for grammar and context.

Lines 47-51: This too long. Separate into two sentences. Learn how to use commas and semicolon in sentences. 

Lines 59-71: There is no flow between these statements and the previous. From the discussions on ascorbic acid and cold storage, the authors hopped to volatile compounds. Revise for flow and grammar.

Lines 71-75: The style of writing is rather poor. The authors should read standard manuscript and appraise themselves of writing styles. The novelty of the study should be appropriately articulated here. For example, the authors can say: “Limited studies exist on the combination of ascorbic acid coating and cold storage for the preservation fresh-cut apples during storage, and to the best of our knowledge, volatile compound formation in ascorbic acid coated fresh-cut apples during cold storage is yet to be evaluated. Therefore, the aim of the study is to evaluate the ……….” This is how to argue novelty. Avoid repetitions.  

Lines 75-77: Revise for grammar. 

Materials and methods

Lines 85-89: What do the authors mean by 50% and 25% coated? Please expatiate. The writing style is poor. This section should be easily reproducible by other researchers, but the write-up is rather ambiguous. Besides, what is the basis of employing different concentration or percentage of coating for the main apple samples and mixed samples? For proper comparison, they should have similar treatments.

Lines 90-91: It is still not clear what the authors mean by distributed by refrigerated container. The authors should learn to write in clear and unambiguous manner.     

Appropriate control (fresh-cut apples without ascorbic acid coating) is still missing in the experimental design. The authors are advised to perform additional experiments for fresh-cut apples without ascorbic acid coating.

Line 111: Start with: For total soluble solids, the fresh-cut apple

The materials and methods section is still poorly written, and the authors are advised to read research articles in standard journals and apprise themselves of the writing styles for the methodology section.

Results and Discussions

I am still not satisfied with discussions presented in the manuscript, as they are rather shallow, without proper discussions on the science behind the results. The authors are advised to present in-depth discussions of the results, the science behind the results, and proper comparison with results of other/similar studies.  

 

Conclusions

The earlier suggestion to revise the conclusions to include/reflect the implications of the results/study for the food industry haven’t been attended to.

 

Comments on the Quality of English Language

Extensive editing of English Language required.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

The paper entitled Volatile Compounds and Quality Characteristics of Fresh-Cut Apples and Mixed Fruits Coated with Ascorbic Acid during Cold Storage after first revision, the paper show lack not clarify and not improved by the Authors. Probably the Authors should deepen better their knowledge of fresh cut products and the relative technologies in order to prolong their shelf life and parameters for characterized the treatment proposed.

 

Possible new title: Volatile Compounds and Quality Characteristics of Fresh-Cut Apples Coated with Ascorbic Acid or stored in mix with Fruit at different temperature

Keywords need to be improve.

The introduction maintains references not specific for the fresh-cut apple in different article section as previously highlighted during first revision (i.e L56-57). Many sentences are not clear and are confused and not in line with high level require for the Journal.

Check in all text: change 0°C with 0° C

A suggest using for the samples analyzed during the trial "fresh cut apple" and not "apple", since in this case the reader can confused with whole apple.

When report the AE, BI and WI parameters report the data of L* a* and b* is pleonastic

L97-98 I suggest to separate in a specific sub paragraph

If choose to use an abbreviation used that in all text after the first time

The ten VOCs compound reported were the only or the more representative?

Fig 1, 2 and 3 are very difficult to read the value reported. Better to report the all parameters in a table.

Fig 7 need to be explain better.

An English Language Editing service, as previously suggested, was not conducted by the Authors.

Apple (Malus × domestica Borkh cv Hongro)

Response 5 of Response to Reviewer 4 Comments need to be report in the introduction to support the temperature chosen during the trial

L106 two g for determine the moisture content is very low, since the sample usable was 150 g for replicate.

In captions explain what means mixed fruits

L312-313 I suggest to rearranged the sentence report in the text as example below reported:

Based on the appearance, the shelf-life was of 30, 18, and 10 days for the sample stored at 4, 8 and 15 °C respectively. Whereas for the sample of fresh cut apple stored at 4 °C with kumquat and tomato was of 3 weeks. Please check and improve in all text in which are present similar sentence in order to obtain a more fluid text.

L312 references in the list is absent

L360 dE or ΔE ? Check in all text.

Comments on the Quality of English Language

An English Language Editing service, as previously suggested, was not conducted by the Authors.

Author Response

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Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study reports on the quality changes of fresh-cut apples coated with ascorbic acid and packed in plastic cups alone and in a mixture with apples, oranges, and tomatoes at various temperatures (4°C, 8°C, 15°C). The results indicate differences in flesh color, browning index, firmness, and total viable count (at an early stage of 4°C storage) between fresh-cut apples alone and mixed products. However, there are no significant differences in moisture content, total soluble solids, titratable acidity, browning index, and pH among different storage temperatures. Firmness, titratable acidity, and pH exhibit a high correlation to microbial growth. The authors conclude that the optimal temperature for extending the shelf-life of fresh-cut apples was 4°C.

 

The work is informative; however, the results are not novel and have been reported in various other studies. Some suggestions are listed below:

There is no rationale and discussion as to why a mixed product is included in this work.

There is no detail on the cultivars of apples, tomatoes, and oranges used.

The concentration of ascorbic acid and other details of ascorbic acid application are not provided.

There is no detail on the experimental design, the number or population size of samples used per replicate.

Equation (1) is incomplete, missing %, and clarification on what sample weight represents. Is it the same as the initial weight?

There is no statistical analysis presented for the graphs.

Lines 107-117 lack an explanation for the absence of differences in physicochemical property changes during storage at 4°C and 15°C.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents the effect of storage temperature on the quality preservation of fresh-cut apples. Based on various parameters evaluated, it demonstrates the advantage of storage at 4°C as compared to 8°C and 15°C. This result is rather obvious, and storage temperatures of 4 or 5°C (that is practically the same) are generally used with fresh-cut apples. See, for example, the paper by Osuga et al. (2021) cited in the manuscript: "Several studies have assessed the quality of fresh-cut apples stored at around 5°C. Therefore, storage at 5°C was selected as the control treatment (Gao, Wu, Zeng, Li, & Guan, 2018; Putnik et al., 2017a; Rocha & Morais, 2003; Wu & Chen, 2013)". Another approach presented in this manuscript, the comparison of fresh-cut apple quality alone and within a mixed product (apple, orange and tomato) is rather arguable because quality can be attributed only to a product as a whole: no matter how certain ingredient is preserved if the others deteriorate. Preservation duration of 30 days reached in this study is a good result, although not outstanding for fresh-cut apples; see for example Kumar, P. and Sethi, S., 2021. Influence of modified atmospheres on shelf life and quality of fresh-cut apples. Journal of Packaging Technology and Research, 5:209-216 that reported with certain products 42 days of storage life at 5°C. Altogether, the manuscript confirms the well-known importance of appropriate storage temperature for product preservation. Therefore, I cannot recommend it for publication due to the lack of novelty.

Comments on the Quality of English Language

The language quality of the manuscript is inconsistent; some sections are OK while others need rigorous editing. Some examples of language inaccuracies are presented below.

·     Mixing plural and singular: "Fresh-cut APPLE IS commonly KNOWN AS minimally processed agriculture PRODUCTS BECAUSE OF THEIR…" (l. 10-11).

·     Inventing non-existing words: "PHYSICOCHEMICALS" (l. 17) and typos "speSification" (l. 76);

·     Incorrect use of words: "Fresh agriculture products are well known as a HIGH SOURCE [instead of "rich source" or "high content"] of essential nutrients for the human body AND CONSIST OF natural functional PROPERTIES SUCH AS PHENOLS, antioxidants, flavonoids, and vitamins [instead of, for instance, "contain natural functional compounds such as polyphenols… etc.]" (l. 24-26);

Sometimes, incorrect use of words inverts the sentence meaning: "PRESERVATION of fresh-cut apples CAN potentially BE RETARDED" (l. 45) with the intention to claim that "deterioration can be retarded" or "quality can be preserved".

Author Response

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Author Response File: Author Response.pdf